Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$164.61	4.631%	$172.2331	$172.23	$172.25	$172.20
Purchase #2	$188.48	4.707%	$197.3518	$197.35	$197.35	$197.40
Purchase #3	$206.61	7.742%	$222.6057	$222.61	$222.60	$222.60
Purchase #4	$161.46	6.668%	$172.2262	$172.23	$172.25	$172.20
Purchase #5	$73.51	12.467%	$82.6745	$82.67	$82.65	$82.70
Purchase #6	$122.82	10.543%	$135.7689	$135.77	$135.75	$135.80
Purchase #7	$49.70	9.799%	$54.5701	$54.57	$54.55	$54.60
7 purchase totals =	$967.19		$1,037.4303	$1,037.43	$1,037.40	$1,037.50